As is well-known, many species of animals and birds are raised and/or kept by people for various purposes, e.g., as pets; for the production of valuable products such as food or furs; or for experimental purposes. A major problem connected with the raising and/or keeping of animals is the disposition of their waste excretions, mainly urine and feces. Whether the animal or bird is caged, in which case its waste is deposited on the floor of the cage, or allowed to roam free but is trained to deposit its waste in a particular receptacle, a “litter” material is generally employed which is capable of absorbing the liquid portion of waste excretions, primarily urine and the excess liquid of fecal matter.
The most commonly used litter box absorbent materials are inexpensive clays, such as calcined clays, that are safe and non-irritating to the animals, and that absorb relatively substantial amounts of liquids. Other porous, solid litter box absorbent materials, that are used alone or in combination, include straw, sawdust, wood chips, wood shavings, porous polymeric beads, shredded paper, sand, bark, cloth, ground corn husks, cellulose, and water-insoluble inorganic salts, such as calcium sulfate. Each of these absorbent materials has the advantage of low cost, but each suffers from the disadvantage of merely absorbing a liquid waste product and holding the product within its porous matrices, or, in the case of sand, absorbing the liquid dross on its surface. For each absorbent material, offensive odors are eventually caused by the absorbed urine, and the entire contents of the litter box, including soiled absorbent material and unsoiled absorbent material, has to be discarded.
In order to reduce or eliminate objectionable odors, homeowners periodically remove the fecal matter from the litter absorbent physically. However, physical removal of the feces does not reduce or eliminate odors caused by the urine absorbed into the absorbent. Therefore, when the odors caused by the absorbed urine become intolerable, the homeowner discards the litter box absorbent material entirely. The homeowner then washes the litter box and refills the litter box with fresh litter box absorbent material. These activities are unpleasant, time-consuming and expensive. Consequently, the litter box absorbent material usually is a relatively inexpensive solid absorbent material, such that an individual cleaning of the litter box is not particularly economically burdensome. However, repeated litter box cleanings over a period of time accounts for relatively large expenditures.
Of particular interest as the basic component of animal litters are the clayey soils or comminuted rocks, e.g. the bentonites, comprising at least one water-swellable clay mineral, e.g., montmorillonite, since these materials have the ability to clump and harden after contact with an aqueous liquid such as urine. This facilitates the removal of only the soiled portion of the litter in a litter box or cage during cleaning without the necessity of removing all the litter.
Many clumping animal litters are made from clays and other mineral substrates. Such litters typically include particles of a mineral substrate, which substrate functions as an absorbent and/or odor reducer. The particles may be coated with a liquid-activated adhesive material, such as gelatinized starch, on the surfaces of the particles. When wetted, the adhesive material is activated and causes the discrete litter particles to agglomerate into clumps.
Although clay-based litters may be functional as clumping animal litters, such litters suffer from certain drawbacks. For example, one disadvantage of clay litters is the high density of the clay component of the litter. Because of this high density, a heavy mass of litter must be used for a given volume of urine. The resulting clumps of spent litter are somewhat heavy, and thus can fracture in the absence of strong interparticle adhesion. Another disadvantage of clay litters is that, because the clay is not biodegradable, the litter cannot be flushed into some sewerage systems after use. This may be inconvenient for certain animal owners.
Clumping litters made from bentonite were introduced in 1989, providing better and longer lasting odor control than did traditional litters. Bentonite is a swelling mineral of the clay category, with a unique ability to gel and agglomerate when wetted, creating scoopable clumps. However, mineral based clumping litter are heavy and dusty. While their innate absorption, clumping, and odor control attributes are good, further performance improvement by solid and/or liquid additives is limited.